This shows that, for the most part, British do believe, by a wide majority.<quoted text>
For the same reason a nonbelieving Jew would check the Jewish box.
It's their family; their background; their heritage; it's the group they identify with. if they have to select, that's the box for them.
My only point is that, regardless of how they identify themselves, Brits and Europeans for the most part don't believe. They aren't bothered with religious beliefs. They are secular.
You may have the last word. Anything else I could say about it now would be repetition.